Wireless communication networks may consist of one or more wireless communication devices (WCD's), and infrastructure in the form of a radio access network (RAN). WCD's may be mobile phones, portable computers, personal digital assistants (PDA's) or any other mobile or fixed computing device with a wireless network interface. A RAN may comprise one or more base transceiver stations (BTS's), one or more base station controllers (BSC's), and backhaul connections between these infrastructure components. The RAN may be connected to other networks such as the Internet, private Internet Protocol (IP) networks, and the public switched telephone network (PSTN).
A BTS may comprise one or more transceivers, which radiate to define wireless coverage areas. These wireless coverage areas are more commonly referred to as cell sites or sectors, and may comprise wireless coverage radiated from a BTS, a plurality of BTS's, or a portion or a single BTS. However, the present discussion is not limited by the inclusion of such terminology. With these wireless coverage areas, BTS's may provide wireless network connectivity to one or more WCD's by allocating portions of their air interface capacities to the served WCD's. The BSC's preferably supervise the operation of the BTS's. A BSC may control when a BTS allocates or de-allocates air interface resources to particular WCD's, and may manage the handoffs of WCD's from one wireless coverage area to another. Regardless of the technology used to create the wireless signals, communication channels that transmit from the RAN to the WCD's are preferably called forward link channels, and communication channels that transmit from the WCD's to the RAN are preferably called reverse link channels.
WCD's may be in communication with one or more wireless coverage areas simultaneously, and a WCD may be receiving forward link signals of different strengths from each wireless coverage area. A group of wireless coverage areas that the WCD is receiving signals from may be called the WCD's “active set,” however a WCD may also receive signals from wireless coverage areas not in its active set. The BTS's that define a WCD's active set may be referred to as the serving BTS's of the WCD. Maintaining communication with multiple wireless coverage areas simultaneously provides advantages for a WCD, including but not limited to making handoffs faster and less disruptive. Therefore, it is desirable for a WCD to maintain a certain threshold of forward link signal strength from the wireless coverage areas in its active set.
A WCD may influence the power of forward link transmissions from the RAN. A WCD may compare the signal strength received from a given wireless coverage area to a threshold. If the received forward link signal strength is too low, the WCD may request the RAN to increase the wireless coverage area's signal strength. This determination can be accomplished by, for example, the WCD measuring the signal-to-noise ratio (SNR) or frame error rate (FER) for the received forward link signal from one or more wireless coverage areas in its active set, and comparing the measured values to a threshold. Depending on the outcome of this comparison, the WCD may request that the RAN increase the power of the forward link signals of the wireless coverage areas in the WCD's active set. The WCD may continue to request that the RAN increase forward link transmission power in the WCD's active set, until the WCD is receiving forward link signals of sufficient strength.
Likewise, if the received forward link signal strength is too high, the WCD may request the RAN to decrease the wireless coverage area's signal strength. The WCD may request that the RAN decrease the power of the forward link signals of the wireless coverage areas in the WCD's active set. The WCD may continue to make this request until the WCD is receiving forward link signals of an appropriate strength.
When the RAN adjusts the forward link power of a wireless coverage area upon an adjustment request from a WCD, the adjustment is typically limited to the forward link channels serving the requesting WCD. Forward link channels serving other WCD's are preferably not directly impacted.
In this way, transmission power of the wireless coverage areas in a WCD's active set may be either increased or decreased so that the system maintains a desired signal quality despite changing conditions.